1. Technical Field
This application relates to a vascular filter and more particularly to a vein filter for capturing blood clots within the vessel.
2. Background of Related Art
Passage of blood clots to the lungs is known as pulmonary embolism. These clots typically originate in the veins of the lower limbs and can migrate through the vascular system to the lungs where they can obstruct blood flow and therefore interfere with oxygenation of the blood. Pulmonary embolisms can also cause shock and even death.
In some instances, blood thinning medication, e.g. anticoagulants such as Heparin, or sodium warfarin can be given to the patient. These medications, however, have limited use since they may not be able to be administered to patients after surgery or stroke or given to patients with high risk of internal bleeding. Also, this medication approach is not always effective in preventing recurring blood clots.
Therefore, surgical methods to reduce the likelihood of such pulmonary embolisms by actually blocking the blood clot from reaching the lungs have been developed. One surgical method of treatment involved major surgery where the size of the vessel lumen was restricted by placement of ligatures or clips around the vein, e.g. the inferior vena cava which transports blood from the lower portion of the body to the heart and lungs. This prevented passage of dangerously large blood clots through the vein to the lungs. However, this approach is an invasive surgical procedure, requiring an abdominal incision and general anesthesia and frequently causing vessel thrombosis and lower extremity swelling. Also, there is a lengthy patient recovery time and additional hospital and surgeon expenses associated with this major surgery. In fact, oftentimes, the patients requiring the surgery are unhealthy and the major surgery and general anesthesia poses a risk in and of itself.
To avoid such invasive surgery, less invasive surgical techniques have been developed. These involve the placement of a mechanical barrier in the inferior vena cava. These barriers are in the form of filters and are typically inserted through either the femoral vein in the patient""s leg or the right jugular vein in the patient""s neck or arm under local anesthesia. The filters are then advanced intravascularly to the inferior vena cava where they are expanded to block migration of the blood clots from the lower portion of the body to the heart and lungs.
These prior filters take various forms. One type of filter is composed of coiled wires such as disclosed in U.S. Pat. Nos. 5,893,869 and 6,059,825. Another type of filter consists of legs with free ends having anchors for embedding in the vessel wall to hold the filter. These filters are disclosed, for example, in U.S. Pat. Nos. 4,688,553, 4,781,173, 4,832,055, and 5,059,205, 5,984,947 and 6,007,558.
Several factors have to be considered in designing vein filters. One factor is that the filter needs to be securely anchored to the internal vessel wall, while avoiding traumatic engagement and damage to the wall as well as damage to the neighboring abdominal aorta. Another factor is that the filter must be collapsible to a sufficiently small size to be easily maneuvered and atraumatically advanced intravascularly to the inferior vena cava or other target vessel. Thirdly, the filter should direct the blood clots to the center of the vessel to improve dissolution of the clot within the vessel by the blood flow.
It would be advantageous to provide a vein filter that satisfies the foregoing parameters. Namely, such vein filter would advantageously have sufficient anchoring force to retain the filter within the vessel while providing atraumatic contact with the vessel wall, would have a minimized insertion (collapsed) profile to facilitate delivery through the vascular system to the surgical site, and would enable migration of the captured blood clots to the center of the vessel. Moreover, it would also be advantageous to provide a filter that could simplify insertion through the femoral or the right jugular vein into the inferior vena cava.
Additionally, the need for a vein filter in many patients is temporary. In these instances it would be advantageous to provide a vein filter that satisfies the foregoing factors and in addition could be readily removed from the patient. It would further be advantageous if the filter could be removed minimally invasively, e.g. intravascularly, and further advantageous if the filter could be removed from the inferior vena cava in either direction, e.g. through femoral access or internal jugular vein access.
The present invention overcomes the disadvantages and deficiencies of the prior art by providing a removable vessel filter comprising first and second filtering portions and first and second anchoring portions. A transverse dimension of the first filtering portion in an expanded configuration is less than a transverse dimension of the first anchoring portion in an expanded configuration, and a transverse dimension of the second filtering portion is less than a transverse dimension of the second anchoring portion. The first and second filtering portions are positioned closer to each other than the first and second anchoring portions, and the anchoring portions are formed on first and second opposite portions of the vessel filter. The vessel filter is removable from a vessel wall by engagement of either the first filtering portion or the second filtering portion.
Removal of the vessel filter by engagement with the first filtering portion removes the filter in a first direction and removal of the vessel filter by engagement with the second filtering portion removes the filter in a second different direction.
In one embodiment the filtering sections are formed by a series of wires and the filter is removable by engagement of at least one of the wires or by engagement of the series of wires by a removal instrument. In another embodiment, the filter is formed by a series of wires, a wire retaining sleeve is positioned at proximal and distal portions of the vessel filter to retain the series of wires, and the vessel filter is removable by engagement of the wire retaining sleeve by a removal instrument.
Preferably a first anchoring member extends from the first anchoring portion and a second anchoring member extends from the second anchoring portion, each of the anchoring members having a first edge to engage the vessel wall and temporarily retain the vessel filter within the vessel. The anchoring member also preferably includes a second sharpened edge opposite the first sharpened edge to engage the vessel wall. The sharp edges engage the vessel wall and temporarily retain the vessel filter within the vessel as the anchoring members are disengagable from the vessel wall to remove the filter as application of an axial force to the filter in the first direction or in the second direction collapses the filter.
Preferably, in the expanded configuration, the transverse dimensions of the first and second anchoring portions are substantially equal and the transverse dimensions of the first and second filtering portions are substantially equal, forming a symmetrical filter for insertion in a first or second direction and removal in the first or second direction. Preferably, each of the filtering portions progressively increases in diameter towards its respective anchoring portion.
The present invention also provides a removable vessel filter comprising a first portion, a second portion and an intermediate portion between the first and second portions. The first portion increases in diameter from the intermediate portion towards a first end and the second portion increases in diameter from the intermediate portion towards a second end. A region closer to the intermediate portion forms a filter portion and the vessel filter has at least one vessel engaging member to temporarily retain the filter within the vessel and allow subsequent disengagement from the vessel wall and removal of the filter.
The filter is preferably formed by at least one wire, wherein the at least one wire forms a part of the first, second and intermediate portions. The at least one wire can be enagaged by a filter removal tool to remove the filter. The filter may further comprise a retaining sleeve at the proximal and distal portions to retain the at least one wire, wherein either of the retaining sleeves are engagable by a removal tool to remove the filter.
The present invention also provides a removable vessel filter comprising a proximal portion forming an anchoring portion, a distal portion forming a filtering portion, a first wire section extending from the proximal portion to the distal portion and forming a series of loops extending substantially in a first direction, a second wire section extending from the proximal to the distal portion and forming a series of loops extending substantially in a second direction different than the first direction, and at least one anchoring member configured to engage the vessel wall and temporarily retain the filter within the vessel. The vessel filter is composed of shape memory material, is movable from a collapsed configuration for delivery to the vessel to an expanded configuration for engagement with the vessel, and is further movable towards the collapsed configuration upon application of an axial force thereto to enable removal of the vessel filter from the vessel.
The anchoring member preferably comprises a tubular member positioned on at least one of the wire sections and has a first sharp end for contacting the vessel wall to temporarily retain the filter. The plurality of wire sections of the vessel filter may be formed by at least first and second separate wires, and the filter is removable by engagement of the at least two wires by a removal tool. The filter can alternatively be removed by engagement of a wire retaining sleeve.
A method of implanting and subsequently removing a vein filter in the inferior vena cava of a patient is also provided comprising:
inserting through a vessel in either a first direction or a second direction a catheter having a filter positioned therein in a collapsed configuration so that wire sections of the filter are in a substantially elongated configuration;
releasing the filter from the catheter to enable the filter to move to an expanded configuration, in the expanded configuration a pair of mounting portions expand to a first diameter and a pair of filter portions expand to a second smaller diameter;
leaving the filter in the vessel for a period of time;
inserting after the period of time in either the first direction or the second direction a filter removal tool to engage at least one of the wire sections; and
moving the tool in a direction opposite the insertion direction of the tool to move the filter towards the collapsed configuration.
In one embodiment, the filter removal tool has at least one movable jaw and the method further comprises the step of actuating the at least one jaw to clamp one of the wire sections. In another embodiment, the wire sections comprise first, second and third wires, the filter removal tool has first, second and third pairs of jaws, and the method further comprises actuating at least one of the jaws of each pair of jaws to clamp each of the first, second and third wires. In another embodiment, the step of inserting a removal tool to engage at least one of the wire sections includes manipulating the filter removal tool so a hook on the tool grasps at least one of the wire sections. The step of manipulating the filter removal tool can include manipulating first, second and third hooks of the tool so that each hook engages one of the first, second and third wires.
In alternate embodiments, the step of inserting the tool to engage at least one of the wire sections comprises the step of engaging at least one of the wire sections with locking barbs of the removal tool or engaging at least one of the wire sections with a collapsible braid of the removal tool to frictionally engage at least one of the wire sections. In another embodiment, the filter terminates in an atraumatic tip and the step of inserting the tool to engage at least one of the wire sections comprises the step of engaging the atraumatic tip.
The present invention also provides a method of implanting and subsequently removing a vein filter in the patient""s inferior vena cava comprising:
inserting through a vessel a catheter having a filter positioned therein in a collapsed configuration so that wire sections of the filter are in a substantially elongated configuration, the wire sections held at a proximal portion by a proximal retaining sleeve and held at a distal portion by a distal retaining sleeve;
releasing the filter from the catheter to enable the filter to move to an expanded configuration, in the expanded configuration a pair of mounting portions expand to a first diameter and a pair of filter portions expand to a second smaller diameter;
leaving the filter in the vessel for a period of time;
inserting a filter removal tool in a first direction after a period of time to engage one of the retaining sleeves; and
moving the tool in a direction opposite the first insertion direction of the tool to move the filter towards the collapsed configuration.
In one embodiment, the filter removal tool comprises a snare, and the method of inserting the tool to engage the retaining sleeve further comprises the step of tightening the snare against the retaining sleeve of the filter. In another embodiment, the filter removal tool comprises a grasper having at least one movable jaw, and the method of inserting the tool to engage the retaining sleeve further comprises the step of actuating the at least one movable jaw to clamp the jaw on the retaining sleeve.
In any of the foregoing methods the filter can be inserted through the internal jugular vein, superior vena cava or through the femoral vein and removed through the internal jugular vein, superior vena cava or the femoral vein. Preferably the methods further comprise the step of delivering cold saline into the catheter to maintain the filter in the collapsed configuration. Preferably, the step of releasing the filter comprises withdrawing the catheter to expose the filter.